<template>
  <div class="spec-preview">
    <img :src="defaultImg.imgUrl" />
    <div class="event" @mousemove="mousemoveHandel"></div>
    <div class="big">
      <img :src="defaultImg.imgUrl" ref="bigImg"/>
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    data() {
      return {
        indexInfo:0
      }
    },
    mounted(){
      this.$bus.$on("changeZoomIndex" , (index) => {
        this.indexInfo = index
      })
    },
    props:["skuImageList"],
    computed:{
      //使用计算属性得到skuImageList[index]项
      defaultImg(){
        return this.skuImageList[this.indexInfo] || {}
      }
    },
    methods:{
      mousemoveHandel(e){
        //得到鼠标到外层元素边缘的距离
        const changeMove = {
          left :  e.offsetX, 
          top : e.offsetY
        }
        //计算蒙版的位置
        let maskMove = {
          x : changeMove.left - this.$refs.mask.offsetWidth / 2,
          y : changeMove.top - this.$refs.mask.offsetHeight / 2,
        }
        //判断临界值
        if(maskMove.x < 0){
          maskMove.x = 0
        }else if(maskMove.x >= e.target.clientWidth - this.$refs.mask.offsetWidth){
          maskMove.x = e.target.clientWidth - this.$refs.mask.offsetWidth
        }

        if(maskMove.y < 0){
          maskMove.y = 0
        }else if(maskMove.y >= e.target.clientHeight - this.$refs.mask.offsetHeight){
          maskMove.y = e.target.clientHeight - this.$refs.mask.offsetHeight
        }

        //赋值
        this.$refs.mask.style.left = maskMove.x + "px"
        this.$refs.mask.style.top = maskMove.y + "px"

        //大图赋值
        this.$refs.bigImg.style.left = -2 *  maskMove.x + "px"
        this.$refs.bigImg.style.top = -2 *  maskMove.y + "px"
      }
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>